Apparatus for stripping fluid from well pipe

ABSTRACT

The apparatus is used in conjunction with a rig to strip mud or oil from a tubular string as it is pulled from a well. The apparatus comprises a pair of opposed, overlapping rubber pads mounted in a container. One or more air cylinders or like means link the pads. The cylinders can be actuated from the rig floor to draw the pads together around the string as it sways laterally during tripping. The pressure with which the pads press against the string can be adjusted; this permits the unit to operate as a stripper when the string is being pulled from the well, and as a well bore cover when the string is being run back into the well.

llitited States Patent [1 1 Brown [54] APPARATUS FOR STRlPPlNG FLUIDFROM WELL PIPE [76] Inventor: William Henry Brown, 13055 149th Street,Edmonton, Alberta, Canada [22] Filed: Aug. 17, 1971 21 Appl. No.:172,423

[52] U.S. Cl. ..15/210 B, 166/82 [51] int. Cl. ..lEZlb 33/08 [58] Fieldof Search ..15/102, 210 B, 104.04;

[ 51 May 22,1973

2,809,012 10/1957 Stevens ..166/82 Primary Examiner-Leon G. MachlinAtt0rneyErnest Peter Johnson [57] ABSTRACT The apparatus is used inconjunction with a rig to strip mud or oil from a tubular string as itis pulled from a well. The apparatus comprises a pair of opposed,overlapping rubber pads mounted in a container. One or more aircylinders or like means link the pads. The cylinders can be actuatedfrom the rig floor to draw the pads together around the string as itsways laterally during tripping. The pressure with which the pads pressagainst the string can be adjusted; this permits the unit to operate asa stripper when the string is being pulled from the well, and as a wellbore cover when the string is being run back into the well.

4 Claims, 7 Drawing Figures PMENTED W 22 SHEET 1 B 5 PAIENIEUM 22 I975SHEET 5 OF 5 APPARATUS FOR STRIPPING FLUID FROM WELL PIPE BACKGROUND OFTHE INVENTION This invention relates to a wiper device for strippingfluid, such as drilling mud, oil or the like, from the exterior surfaceof a well string. 7

In oil field operations, a well string is usually disposed within thebore of a producing or drilling well. In the case of the well beingdrilled, the string may comprise a bit, drill collars and drill pipe. Inthe case of a producing well, the string may comprise tubing or suckerrods. The expression well string, as used herein, is intended to coverthe various strings which may be present in a well bore and which areperiodically tripped by a rig. It is to be noted that any one of thesewell strings is comprised of parts of different outside diameter; forexample, a typical drilling string might have a 12 1 inch O.D. bit, 6 Ainch O.D. drill collars and 4 Va inch O.D. drill pipe.

When the well string is drawn or tripped out of the well bore, a fluidcoating usually adheres to the strings outer surface. In the case wherethe well is being drilled, this fluid is usually drilling mud; in thecase of a producing well, the fluid is normally oil. It is standardpractice to strip or wipe this fluid from the string at the well head.If this is not done, the fluid drops on the rig floor and makes it tooslippery to work on. In addition, the fluid often has substantial valueand it is therefore desirable to conserve it within the well bore or mudtank system.

Up to the present time, it has been conventional to use a rubber collarfor stripping. This collar is brought into operation by removing therotary bushing in the rigs floor, threading the collar over the upperend of the string, and working it down until it seats on the annularshoulder of the bushing bore. The heavy bushing is then replaced in thebore to hold the collar in place around the string. The stationarycollar tightly embraces the string and wipes it clean as it is pulledthrough it.

The rubber collar is characterized by some shortcom ings in its role asa wiper. For example, the insertion and removal of the collar aretime-consuming and expensive operations. The collar is not adapted topermit the passage of the large diameter tools, such as ream ers,stabilizers and bits, which are normally present in a drilling string;hence the collar must be removed before these tools are reached. Sincethe collar is fixed by the bushing, it cannot move or float sidewayswith the string when it sways back and forth during a trip. As a result,a portion of the strings circumference is often left unwiped. The fluidwhich is stripped from the string is not contained in any way andsplashes on the rig substructure and blow-out preventer. This makes amess which has to be cleaned up. When the string is out of the well, thewell bore is open and metal objects can drop into it and cause futuredrilling problems. Along the same line, the collar is usually not usedwhen tripping back into the well; as a result, metal objects can fallinto the open annular space between the well string and bore wall.

SUMMARY OF THE INVENTION It is an object of this invention to provide awiper device having enclosed wiper pads which remain permanently inplace over the well head during rig operations and which can be actuatedfrom the rig floor to close about the well string with a selectedpressure, either when pulling out of the well or running back into it.It is a further object to provide a device which is adapted to permitthe passage of large diameter tools while still wiping them dry.

It is another object to provide a wiper device of this type having padswhich can be closed across the well bore when the string is in the rigderrick, so as to prevent foreign objects falling into the well bore.

It is another object to provide a wiper device constructed so that thepassage of enlargements in the string through the wiper pads will causethe pads to move apart, but without any substantial increase in thepressure with which the pads press against the string.

It is another object to provide a wiper device which is capable ofstripping odd-shaped joints present in the string, such as the Kellyjoint.

It is another object to provide a compact unit which will fit within thenarrow confines of a rigs substructure.

It is another object to provide a wiper device which is simple to buildand maintain and which does not become easily jammed by the caking ofdrilling mud therein.

It is another object to provide a wiper device which can be adjusted tosatisfactorily strip strings of substantially different outsidediameters, such as drill collars and sucker rods.

It is another object of this invention to provide a wiper device havinglaterally movable wiper pads and actuating means mounted on and linkingthe pads for opening and closing them, whereby the pads and actuatingmeans can move laterally as a unit with the well string when it swaysfrom one side to another.

In accordance with the invention, a pair of overlapping wiper pads arepositioned within a container. The container has aligned top and bottomapertures, which permit of the passage of the well string therethrough.It is adapted to be mounted on the upper end of the rigs conductor pipe,the well pipe or the well head (all hereinafter referred to as the wellhead), and functions to trap stripped fluid so that the fluid will flowback into the well head. The wiper pads are spaced from each of thecontainer side walls and are thus free to move in a horizontal plane.Each wiper pad comprises a rubber block sandwiched between two U- shapedplates. The block has a generally horseshoeshaped opening formed in itsinner edge. When the pads are pressed against the well string, theopposed faces of the two block openings conform to the string surfaceand wipe its full circumference dry. A pair of double-acting cylindersare mounted on and link the pads. Each cylinder is disposed along onelongitudinal edge of the pad structure and has its piston attached toone pad and its barrel attached to the other. Actuation of the cylindersdraws the pads toward each other longitudinally or forces them apart.Flexible air hoses or conduits connect each end of each cylinder with asource of pressurized air or like fluid. A valve, preferably located onthe rig floor, is provided to control the supply of air to the lines soas to direct air into either end of each cylinder so that they can beexpanded or contracted to adjust the positions of the pads. Anaccumulator tank is provided in the air line for closing the pads. Whenan enlargement, such as the bit, forces the pads apart, the back flow ofair is absorbed in the accumulator tank with no significant increase inpressure.

The device has certain advantageous features. More specifically, theresultant structure is operative for most well strings and yet is simpleand compact enough to fit within the sub-structure of small drillingrigs. The pads, with the air cylinders mounted on them, are notrestrained from lateral movement; they can float with the string andcontinuously wipe its entire circumferential surface. Because thepressure applied to the pads can be varied, the unit can be used duringtripping in both directions (the pressure applied when running in withdry pipe should be less than that when pulling wet pipe). The provisionof the accumulator tank permits the pads to accomodate the passage of a4 /2 inch O.D. drill pipe or a 12 A inch O.D. bit without damage.Without the tank, the increase in operative pressure occastioned by thepassage of the bit would subject the rubber pads to severe wear andpossible tearing. When the string passes out of the unit, the padsautomatically move to a fully closed condition, thereby bridging thewell bore and providing a hole cover. If it is desired to open the padsto a fully open position, this can easily be done by reversing the airpressure to the opposite ends of the cylinders. The container serves tocatch the oil or mud which has been stripped and directs it back intothe well head; the rig sub-structure is thus kept clean and there islittle or no pollution due to oil or oilbase mud dropping onto theground.

Broadly stated, in a wiper device for stripping fluid from the outersurface of a well string, which device comprises a container having sidewalls, a pair of horizontal wiper pads disposed within the container andslidable between an open position, wherein they are disassociated fromthe well string, and a closed position, wherein they press against thewell string, the invention comprises the following improvement: acontainer having side walls which are outwardly spaced from the sides ofthe wiper pads to permit of lateral movement of the pads therewithin; atleast one cylinder assembly mounted on and linking the wiper pads foropening and closing them; and flexible means, connected to the cylinderassembly, for supplying operating fluid to it.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a top view ofa portion of the preferred form of the device;

FIG. 2 is a side view of the device of FIG. 1, showing a well stringpassing therethrough;

FIG. 3 is a side view of the device of FIG. 1 incorporated into a rigstructure;

FIG. 4 is a side view of another embodiment of the device, showing itmounted on the well head;

FIG. 5 is a perspective view of part of the embodiment shown in FIG. 4;and

FIG. 6 is a side view of the device of FIG. 4 shown in place within asub-structure of a drilling rig; and

FIG. 7 is a top view ofa wiper pad used in the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT The Container As illustrated inthe drawing, the container 1 is boxlike in form and has top, bottom andside walls 2, 3 4. aligned openings 5, 6 are provided in the top andbottom walls 2, 3. The bottom opening 6 is slightly smaller in diameterthan the well head 7 so that a shoulder 8, which seats on well head 7,is provided. A skirt element 9 extends downward from bottom wall 3. Thiselement 9 has an inwardly curved section 10, which, in combination withthe well head 7, defines an annular chamber 11. An inflatable gasket 12is disposed within the chamber 11 for sealing the device to the wellhead 7. A depending section 13 extends downward from the curved section10 and has openings therethrough for receiving lock screws 15. Thescrews 15 fix the container l on the well head 7.

In operation, the container 1 functions to trap the fluid which isstripped, so that it can drop back into the well head 7.

The Wiper Pads The upper and lower wiper pads 16a, 16b each comprise anelastic, resilient block 17 sandwiched between a pair of U-shaped plates18, 19. The three parts are bonded together to form a solid unit.

The block 17 is suitably formed of neoprene rubber. One suitable blockhas a width of 18", length of 16", thickness of 1", and is made ofmaterial having the characteristics listed in Table I.

TABLE I Hardness, ASTM D-2240, A Durometer 50 Tensile strength, ASTMD-4I2, psi 2500 Ultimate elongation, ASTM D-4l2, percent 450 Tear test,ASTM D-624, Die C, lbs./lin.inch 250 psi Accelerated aging test, ovenaged hrs./2l2F, ASTM D-573 Hardness, A Durometer max. change 15 pointsTensile strength max, change 15 percent Elongation at break max. change40 percent Compression set, ASTM D-395 22 hrs./l58F, Method percent max.deformation 25 percent.

The block 17 defines a horseshoe shaped groove or opening 21 in itsinner edge. The opening 21 is cut so that the block 17 will conform tothe surface of the well string 22 when pressed thereagainst. A pair ofopposed blocks 17, having an opening 21, as shown in FIG. 7, with aradius of 2 inches are adapted to wipe almost any well string in commonuse at this time. As shown in FIGS. 1 and 2, the container 1 has sidewalls 4 which are spaced outwardly from the sides of the wiper pads 16a,16b to permit of lateral movement of the pads.

The Cylinders Biasing means, such as the double-acting air cylinderassembly 23, links the two wiper pads 16a, 16b. Each assembly 23includes a piston 24 and barrel 25. The piston 24 is connected, by a pinand yoke assembly 26, with a lug 27 extending up from the lower wiperpad 16b. The barrel 25 is connected, by a collar 28, to the upper wiperpad 16a. Expansion of the cylinder assemblies 23 will slide the pads16a, 16b apart to the open position against the side walls 4 of thecontainer 1. Contraction of the assembly 23 will slide the pads 16a, 16bto a closed position wherein they press against the well string 22. Whenthe well string 22 is pulled out from between the pads 16a, 16b, furthercontraction of the assemblies 23 will cause the pads to overlap to suchan extent that they provide a closure or cover over the well bore.

Means for Supplying Closing Force The cylinder assemblies 23 areactuated by an air system. This system comprises a source 30 ofpressurized air, first and second flexible air lines 31, 32 connectingthe source 30 with the assemblies 23, and an accumulator tank 33connected into the first or closing air line 31. The rig is usuallyequipped with an air compressor to provide the air source 30. If not, abottle of compressed air can be provided on the rig floor. A five-wayvalve 34 is connected to the air source 30 for directing the air flowinto one or the other of the two air lines 31, 32 and bleeding off theline which is not being used. The first air line 31 connects the valve34 with one end of the cylinder assembly 23 whereby, when air isintroduced to the line 31, the piston 24 telescopes into the barrel andmoves the pads 16a, 16b together. The second air line 32 connects thevalve 34 with the other end of the cylinder assembly 23 so that when airis admitted thereinto the said assembly is expanded. By controlling theair pressure, the closing force exerted on the pads 16a, 16b can bevaried.

An accumulator tank 33 is connected into the first air line 31, as shownin FIG. 2. When an enlargement in the well string 22 passes through thewiper pads 16a, 16b and forces them apart, the accumulator tank 33receives the air displaced. The pressure within the cylinder assemblies23 is maintained at a substantially constant amount by the absorption ofthe small volume of displaced air into the large volume of air withinthe tank 33.

Alternative Embodiment An alternative embodiment of the wiper device isshown in FIGS. 4, 5, 6. In this embodiment, the container l and wiperpads 16a, 16b are the same as those in the previously described version.However, the means for opening and closing pads 16a, 16b are somewhatdifferent. Such means involves a system of cables and sheaves. For easeof description, only one cable and sheave assembly is describedhereinbelow, although it is preferred to provide two assemblies, one oneach side of the wiper pads.

More particularly, a cable 35 is attached at its first end to the frontportion of upper wiper padl6a and at its other or second end tothe-front portion of lower wiper pad 16b. The cable 35passes over thesheaves 36, 37 mounted within the container 1, and then extends throughthe opening 38 to the movable member 39, which is disposed outside thecontainer 1. .The cable 35 passes around the sheave 40, which is mountedon movable member 39, and returns through opening 38 and over containersheave 41 to wiper pad 16b. With this arrangement, when well string 22shifts the pad 16a to the right, the first end of cable 35 is drawn tothe right, thereby causing the second cable end and its attached wiper16b to also move the same distance to the right. In other words, thecable and sheave arrangement link the wiper pads together so that theymove as a unit with the swaying well string.

The moveable member 39 is connected through a spring and cablecombination 42 with means 43 adapted to supply a closing force foractuating the pads 16a, 16b. In greater detail, the member 39 isconnected to a length of cable 420 which is connected with a spring 42bat its other end. The spring 42b is, in turn, connected to an aircylinder 43 by a second length of cable 420. The air cylinder 43 issupplied with pressurized air through an airline 44 having a controlvalve 45 at the rig floor. The air line 45 is suitably tied in with theair supply on the rig.

Springs 46 are attached at one end to each of the wiper pads 16a, 16band at the other end to the rig structure 47. These springs 46 act tonormally urge the pads 16a, 16b to the fully open position.

In operation, the return springs 46 are set with a pressure such as .60lbs. Pressurized air is then admitted to the air cylinder 43 to pull themember 39 down and partly stretch the spring 42b so as to overcome thetension of the return springs 46 and exert a pressure with each pad 16a,16b of about lbs. The wiper pads 16a, 16b, whose weight might be about60 pounds, tightly embrace the well string 22 and are lifted slightlyoff the container bottom wall 3 when the well string is passingtherethrough. The pads 16a, 16b float with the string 22. When anenlargement in the string forces the pads 16a, 16b apart, the member 39is drawn upwards. However, there is no significant increase in pressureinvolved, since the spring 42b stretches to accommodate this movement.When the well string 22 is lifted out from between the pads 16a, 16b,the pressure on the said pads causes them to further overlap so as toprovide a closure. When the air pressure is released, the return springs46 automatically draw the pads 16a, 16b to the fully open position.

Important Features The device is controlled from a convenient location,such as the rig floor. The number of parts within the container are keptas small as possible so that its outside dimensions are small; as aresult, it can be accomodated within the limited space available in therig sub-structure. The wiper pads literally float with the well stringso that there is little wear. The pads can undergo several inches ofwear and still remain operative. There is provision for the passing ofstring enlargements through the pads without severe pressure increase.The mud or oil which is stripped is retained and returned to the wellhead. The pads can provide a closure across the well bore and preventforeign objects falling into it. The adjustability of the closing forceor pressure enables the pads to be closed when the well string is beingtripped in either direction. When the string is being run in, the padsfunction to deflect gas kicks. By having these features in combination,the device is a practical and workable tool.

What is claimed is:

1. In a wiper device for stripping fluid from the outer surface of awell string, which device comprises a container having side walls, apair of horizontal wiper pads disposed within the container and slidablebetween an open position, wherein they are disassociated from the wellstring, and a closed position, wherein they press against the wellstring,

the improvement which comprises:

said container having side walls which are outwardly spaced from thesides of the wiper pads to permit of lateral movement of the padstherewithin;

at least one cylinder assembly mounted on and linking the wiper pads foropening and closing them; and

flexible means, connected to the cylinder assembly,

for supplying operating fluid to it.

2. The improvement as set forth in claim 1 wherein:

the cylinder assembly is double-acting and has a piston working within abarrel;

and the flexible means comprises two flexible conduits, one connectedinto each end of the barrel.

3. The improvement as set forth in claim 2 comprising:

a source of pressurized air;

first and second air lines, each connecting the source with one of theflexible conduits;

and accumulator means in the first air line for receiving air, displacedfrom the cylinder assembly due to the passage of an enlargement throughthe wiper pads, and maintaining the pressure substantially constantwithin the cylinder assembly.

4. A wiper device for use in conjunction with a rig working on a well,said device being adapted to strip fluid from the outer surface of thewell string as it is pulled from the well, comprising:

a container adapted to be mounted on the well-head, said containerhaving top, bottom and side walls with aligned openings formed in thetop and bottom walls for accomodating the passage therethrough of a wellstring;

a pair of wiper pads arranged in horizontal, overlapping, longitudinallymovable relationship within the container, said pads being inwardlyspaced from the side walls and being slidable between an open position,wherein they are disassociated from the well string, and a closedposition, wherein they press against the well string or overlap to forma closure should the well string be out of the well,

each said pad having an elastic, resilient block defining astring-conforming opening in its inner edge;

first means, connected to the two wiper pads, adapted, when subjected toa closing force, to bias them to the closed position, said first meanscomprising a cable, a plurality of sheaves, and a movable memberdisposed outside the container,

one said sheave being mounted within the container and secured thereto,

another said sheave being mounted on the movable member,

said cable being attached at one end to one wiper pad and at the otherend to the other wiper pad, said cable further passing over thecontainer and movable member sheaves whereby, when the well string swayslaterally within the container, the wiper pads are both caused to floatwith it; and

second means, connected to the first means, adapted to supply a closingforce of selected intensity to them, said second means comprising aspring and cable combination connected at one end to the movable member,and

means connected to the said combination at its other end, said meansbeing adapted to supply the said closing force.

1. In a wiper device for stripping fluid from the outer surface of awell string, which device comprises a container having side walls, apair of horizontal wiper pads disposed within the container and slidablebetween an open position, wherein they are disassociated from the wellstring, and a closed position, wherein they press against the wellstring, the improvement which comprises: said container having sidewalls which are outwardly spaced from the sides of the wiper pads topermit of lateral movement of the pads therewithin; at least onecylinder assembly mounted on and linking the wiper pads for opening andclosing them; and flexible means, connected to the cylinder assembly,for supplying operating fluid to it.
 2. The improvement as set forth inclaim 1 wherein: the cylinder assembly is double-acting and has a pistonworking within a barrel; and the flexible means comprises two flexibleconduits, one connected into each end of the barrel.
 3. The improvementas set forth in claim 2 comprising: a source of pressurized air; firstand second air lines, each connecting the source with one of theflexible conduits; and accumulator means in the first air line forreceiving air, displaced from the cylinder assembly due to the passageof an enlargement through the wiper pads, and maintaining the pressuresubstantially constant within the cylinder assembly.
 4. A wiper devicefor use in conjunction with a rig working on a well, said device beingadapted to strip fluid from the outer surface of the well string as itis pulled from the well, comprising: a container adapted to be mountedon the well-head, said container having top, bottom and side walls withaligned openings formed in the top and bottom walls for accomodating thepassage therethrough of a well string; a pair of wiper pads arranged inhorizontal, overlapping, longitudinally movable relationship within thecontainer, said pads being inwardly spaced from the side walls and beingslidable between an open position, wherein they are disassociated fromthe well string, and a closed position, wherein they press against thewell string or overlap to form a closure should the well string be outof the well, each said pad having an elastic, resilient block defining astring-conforming opening in its inner edge; first means, connected tothe two wiper pads, adapted, when subjected to a closing force, to biasthem to the closed position, said first means comprising a cable, aplurality of sheaves, and a movable member disposed outside thecontainer, one said sheave being mounted within the container andsecured thereto, another said sheave being mounted on the movablemember, said cable being attached at one end to one wiper pad and at theother end to the other wiper pad, said cable further passing over thecontainer and movable member sheaves whereby, when the well string swayslaterally within the container, the wiper pads are both caused to floatwith it; and second means, connected to the first means, adapted tosupply a closing force of selected intensity to them, said second meanscomprising a spring and cable combination connected at one end tO themovable member, and means connected to the said combination at its otherend, said means being adapted to supply the said closing force.